Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $41.63   12.161%   $46.6926   $46.69   $46.70   $46.70  
  Purchase #2 $71.26   7.326%   $76.4805   $76.48   $76.50   $76.50  
  Purchase #3 $94.93   10.301%   $104.7087   $104.71   $104.70   $104.70  
  Purchase #4 $115.78   3.513%   $119.8474   $119.85   $119.85   $119.80  
  Purchase #5 $93.51   6.678%   $99.7546   $99.75   $99.75   $99.80  
  Purchase #6 $176.39   12.566%   $198.5552   $198.56   $198.55   $198.60  
  Purchase #7 $228.30   4.200%   $237.8886   $237.89   $237.90   $237.90  
  7 purchase totals = $821.80       $883.9276   $883.93   $883.95   $884.00